London is the largest city in the United Kingdom at a population of 13 million, and it is famous for its extensive London Underground (Tube) network and the iconic traditional Routemasters that were once common in public service. London Buses is part of Transport for London, which in turn is directly governed by the Mayor of London.

Privatization during the 1990s and its subsequent competitive tendering system has made bus operations in London a very dynamic scene - a sizable portion of operators are subsidiaries of foreign-owned conglomerates, and only one of the 12 original operators (Metroline) formed in 1989 has survived under its current name. Fierce competition has led a few big players to exit the London Buses scene altogether, including National Express, Veolia Transdev, and FirstGroup. Under the current system, operators bid for individual bus routes, acquire depot space and procure their own bus fleet subject to TfL requirements. As these practices are capital-intensive, in recent years merger and acquisitions has been largely the choice for new entrants to enter the scene. In most cases, operators own multiple bus companies while adopting a single unified identity. London Buses is used to some extent as a case study by Land Transport Authority in implementing Singapore's competitive bus tendering model from 2016.

Before the new millennium arrived, the traditional Routemaster, Leyland Titans, MCW Metrobuses, Dennis Darts and Volvo Olympians once formed the staple fleet of London Buses. New accessibility requirements forced the retirement of these buses in favour of various low-floor buses from TransBus International (now Alexander-Dennis), Plaxton, East Lancs, Wrightbus, and other local manufacturers. Hybrid buses including the new Routemaster increasingly form the London bus fleet in more recent years. Many of the older buses continue to operate elsewhere in the United Kingdom, where bus operations are completely deregulated. Double-deck buses in London have two axles instead of three, and are of a shorter wheelbase as compared to those in the Far East.

Buses in London has also been a major subject of municipal politics. Under Mayor Ken Livingstone, Mercedes-Benz Citaro G buses replaced almost all of the traditional Routemasters, an act that proved unpopular especially after incidences of fire involving these articulated buses were reported. Boris Johnson made the removal of these Citaro G buses in favour of a modern Routemaster bus design part of his campaign, which he succeeded and ousted Ken Livingstone from office in the 2008 mayoral elections. Boris Johnson went on to introduce the New Bus for London, the spiritual successor to the iconic Routemaster, while retiring the entire Citaro G fleet from service in London.